1. Technical Field
The present invention relates to a system and a method for controlling a speed of a motor, and more particularly, to a system and a method for controlling a speed of a motor capable of maximizing efficiency of a motor by simultaneously controlling a duty value and a phase value in controlling a speed of a motor.
2. Description of the Related Art
As a method for controlling a speed of a motor, there are an open loop control method and a closed loop control method. As the open loop control method does not detect a current speed of a motor, the open loop control method may not accurately control the speed of the motor due to a change in surrounding environment. On the other hand, the closed loop control method may maintain a constant speed at all times as the control of the speed adaptively reacts to the surrounding environment. According to the related art, a method for controlling a speed of a motor based on a duty has been used. However, the method may not implement a maximum efficiency according to characteristics of a motor.
FIG. 1 is a diagram illustrating an example of a system for controlling a speed of a motor based on a closed loop control method according to the related art.
As illustrated in FIG. 1, the system for controlling a speed of a motor according to the related art is configured to include a speed measurement unit 107, a comparison unit 102, a speed control unit 103, a limiting unit 104, and a PWM generation unit 105.
As described above, when the system for controlling a speed of a motor according to the related art intends to control the speed of the motor based on the PWM, the speed of the motor becomes lowest when the duty is 0% and the speed of the motor becomes highest when the duty is 100%. Even though the PWM generation unit 105 applies the PWM of duty 100% to a motor 106, the speed of the motor may be controlled no longer when the speed of the motor 106 does not reach a reference speed 101. Generally, there are many cases in which the maximum speed of the motor 106 may be limited at the time of controlling the speed of the motor only with the duty value. That is, as the control results of the speed control unit 103, the maximum duty is physically 100% even though the duty over 100% comes out, such that the limiting unit 104 limits the duty value within a range of 0 to 100%. Therefore, there is a problem in that the efficiency of the motor may not be maximized.